1. Field of the Invention
The present invention relates to a light source apparatus.
2. Description of the Related Art
Currently, a fiber light source combining a small solid-state light source and an optical fiber is developed. The fiber light source is used as a light source apparatus irradiating light from a tip of a thin structure.
Such a light source apparatus is disclosed by, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-286234. In Jpn. Pat. Appln. KOKAI Publication No. 10-286234, an endoscope apparatus mounted with a fiber light source apparatus combining a laser light source and a diffuser is proposed.
A fiber light source apparatus 1 shown in FIG. 7 includes an He—Cd laser 20 having a trichromatic laser and an He—Ne laser 21 having a red laser. Laser light emitted from the lasers 20, 21 is guided up to a tip end portion of an endoscope 2 by a light guide 10 to irradiate an irradiation object, for example, a living organism 4 via a diffuser 11 and an illuminance distribution adjustment filter 12. In general, the light intensity of solid-state light source light including laser light as a typical example is strong on the optical axis and weak in the periphery of the optical axis. Because a solid-state light source light has coherence, a spot pattern of light called a speckle may arise on the irradiation object. These characteristics are not desirable for a light source apparatus intended for illumination. Thus, Jpn. Pat. Appln. KOKAI Publication No. 10-286234 realizes desired illumination light by laser light being diffused by the diffuser 11. That is, a light source apparatus capable of illuminating a thin lumen such as the endoscope 2 is enabled as a light source apparatus from which a desired illuminance distribution is obtained.
In the fiber light source apparatus 1 proposed in Jpn. Pat. Appln. KOKAI Publication No. 10-286234, laser light emitted from the light guide 10 irradiates the diffuser 11. The diffuser 11 has a function to diffuse and emit laser light forward. In this case, accompanying the diffusion, a portion of the laser light is also radiated backward, that is, to the side of the light guide 10. The laser light radiated backward becomes not only a loss, but also heat after being absorbed into the endoscope 2. That is, there is a possibility that the illumination light becomes darker and the temperature of the tip end portion of the fiber light source apparatus 1 rises. As a result, therefore, there is a possibility that the utilization efficiency of light is degraded near the diffuser 11.